OpenShot Video Editor: different aspect ratios in the same video, and one method of dealing with 'em

One annoyance I've encountered in screen recording gameplay of Total Annihilation is that the menu has a different aspect ratio to the gameplay (if you adjust it, as I did, to 1280x720), so if you record both you need to separate the footage from the menu, and end screens, and adjust the picture so it fills the frame.

At least that's how I've gotten it to work. Perhaps there's a better way, but I don't know it yet and this is the one I figured out and I'm sharing it with anyone who might find it useful. If you know better, I'm sure I'll see it in the comments eventually.